article: May 27 2005 - Rainstorm-induced Landslides in the Bay of Plenty

Heavy rain on Wednesday 18 May in the Bay of Plenty caused disruption to the community with flooding and landslides creating significant problems that resulted in a state of emergency being declared by the Tauranga City Council and for the Matata area by the Whakatane District Council.

Landslide damage in Otumoetai, Tauranga.

The wider region was affected by heavy rainfall with flooding reported along the Bay of Plenty coast from the Coromandel Peninsula to the Rangitikei Plains.

The landslide damage was severe in two urban areas of the Bay of Plenty (Tauranga and Matata) where extreme rainfall was recorded.

In response to this event the Institute of Geological and Nuclear Sciences organised a landslide response through the GeoNet Project.

Two landslide experts went to the area to inspect the damage and provide support to the local emergency management effort as required.

Flying to obtain oblique aerial photographs of the affected areas has also been scheduled to help document the damage.

Clean-up operations under way in Matata on the Awatarariki Stream debris flow fan on the western side of Matata.

In Tauranga multiple landslides occurred in Otumoetai, at Welcome Bay and on Mount Maunganui (Mouao).

The landslides in Otumoetai undermined houses at the top of slopes and the debris damaged houses at the toe of the slopes.

Clean up operations under way on the Waitepuru Stream debris flow fan on the southern side of Matata.

Local geotechnical engineers played a significant role in managing the emergency with experts advising on the landslide damage in Tauranga and instigating immediate mitigation measures to divert stormwater away from landslides and other potentially susceptible areas.

An Urban Search and Rescue (USAR) team was deployed by the New Zealand Fire Service to Tauranga to assist in the recovery operations by shoring up severely damaged homes so residents could return to retrieve valuable possessions.

Landslides from the steep valley walls of the small stream catchments around Matata resulted in debris flows forming and depositing material onto the Rangitakei Plains and the coastal land west at Matata.

The debris flows from Awatarariki Stream caused structural damage to buildings on at least thirty properties and caused flooding damage to another twenty.

The debris flows from the Waitepuru Stream catchment caused structural damage to nine properties with at least another forty affected by flood damage.